DESCRIPTION (adapted from application abstract): Cyclospora cayetanensis is a newly recognized cause of endemic and epidemic diarrhea throughout the world. When the organism was first recognized in 1985, it was thought to be a protozoan (called crypto grande) or a cyanobacterium-like body (CLB) or a blue green alga, because of its autofluorescence. The organism was confirmed to be a coccidian at the University of Arizona in 1993 when it was induced to sporulate. Since then, Cyclospora continues to be recognized as an important cause of diarrhea and malabsorption in a number of developing countries. It also has been recognized as a cause of epidemic disease in the U.S. For example there was a well-publicized outbreak in 1996 involving Florida and 13 other states, possibly associated with imported raspberries. Efforts to understand the pathogenesis and epidemiology of Cyclospora have been limited by the inability of investigators to grow the organism in the laboratory. Little is known about modes of transmission or potential reservoirs of infection, resulting in the lack of adequate approaches for prevention and control of outbreaks. Investigators at the University of Arizona have the potential to develop more information about Cyclospora because of their association with the Cyclospora epidemiology project with the ICIDR site in Peru, and their access to numerous epidemiologically characterized isolates. The investigators plan to apply the techniques of PCR amplification of DNA from small numbers of organisms to the development of a sequence-based approach to the molecular epidemiology of Cyclospora infections. The ITS1 region between the small subunit ribosomal (r)DNA and 5.8S rDNA genes will be amplified, sequenced, and compared for a variety of epidemiologically characterized isolates. These isolates will be obtained from severely ill and asymptomatic patients, human immunodeficiency (HIV)-infected patients and from the 1996 U.S. outbreak. The technique then can be applied to prospective studies of the epidemiology of Cyclospora infections.